1. Field of the Invention
The present invention relates to a semiconductor chip assembly, and more particularly to a semiconductor chip assembly with a contact terminal and its method of manufacture.
2. Description of the Related Art
Semiconductor chips have input/output pads that must be connected to external circuitry in order to function as part of an electronic system. The connection media is typically an array of metallic leads (e.g., a lead frame) or a support circuit (e.g., a substrate), although the connection can be made directly to a circuit panel (e.g., a mother board). Several connection techniques are widely used. These include wire bonding, tape automated bonding (TAB) and flip-chip bonding.
The semiconductor chip assembly is subsequently connected to another circuit such as a printed circuit board (PCB) or mother board during next level assembly. Different semiconductor assemblies are connected to the next level assembly in different ways. For instance, ball grid array (BGA) packages contain an array of solder balls, and land grid array (LGA) packages contain an array of metal pads that receive corresponding solder traces on the PCB.
BGA packages typically have the solder balls fused on land metal elements such as nickel terminals. Since the solder balls are contact terminals to the next level assembly, the BGA package becomes degraded or inoperative when the solder balls separate from the land metal elements.
Conventional solder ball attachment techniques focus on allowing the solder ball to be easily fused on the land metal element. For instance, sequentially plating nickel and gold films on a smooth and flat surface of a land metal element allows the solder ball to be easily fused to the land metal element, however this does not avoid the solder ball separation problem.
Conventional solder ball attachment techniques also focus on contacting an insulator such as bismaleimide triazine epoxy to the solder ball in order to enhance the mechanical attachment of the solder ball. However, the solder ball easily separates from the epoxy as well as the land metal element.
In view of the various development stages and limitations in currently available semiconductor chip assemblies, there is a need for a semiconductor chip assembly that is cost-effective, reliable, manufacturable, versatile, provides a contact terminal with excellent mechanical and electrical properties, and makes advantageous use the particular connection joint technique best suited for a given application.